Yamaha had an alternative to the pucks. Using a rubber ring.
Years ago, i filled the space between disc and hub with some thick plastic, works fine!
The retro fit kit is just a replacement kit of the existing parts 1-6 and utilizing part 3, (oring), instead of part #7. Buy or don't buy the $5 NOS o'ring i linked to or not. The other parts in the Retro kit may be found by doing a search with their part #'s or your 40 year old ones may be perfect so no need to look.
Now? The Andy Griffith Show's on MyTV for 10 more minutes and Ole Barn's on the trail of a robber@jpdevol when you get in here,